1. Field of the Invention
The present invention relates generally to semiconductor fabrication systems and, more particularly, to integrated maintenance scheduling systems.
2. Description of Related Art
Equipment used in the semiconductor manufacturing industry can be extremely expensive and complicated. Engineers must typically execute preventive maintenance (PM) by following standard operation procedures (SOPs) to ensure reliability and stability of the manufacturing equipment. Because of the wide variety and large numbers of equipment, managing the maintenance of equipment manually can be inefficient. Mistakes arising from manual management as well as any lack of completion of the required maintenance procedures can cause equipment failure and can delay schedules of production, thus decreasing enterprise profits.
Manual processes of implementing PM have included paper documents or application software on the managers' personal computers for carrying out the various periodic or aperiodic maintenance plans for all equipment. The engineers, in turn, would execute the maintenance according to the maintenance plans. The maintenance plan typically consisted of preparing the PM sheet that described the maintenance items and of executing the items on the PM sheet. When the engineer completed the maintenance, the engineer would record the data on the PM sheet and send the PM sheet to the manager for review and cosigning. Finally, the engineer would put the PM sheet into a folder as a reference record. When the result of a maintenance item was a failure, the engineer would fill in an Out of Control Active Process (OCAP) provision on the PM sheet.
Many undesirable traits can be associated with the aforementioned manually driven processes. Without integrating with other computerized information systems, it is easy to get data inconsistencies that can affect the quality of maintenance. Moreover, manual processes can be time-consuming. Most equipment has an interface that a PC user can use to communicate with the equipment and get the parameters of the equipment. The parameters of the equipment can be key factors in determining whether or not to execute the maintenance. Maintaining equipment requires time of an engineer for approaching the equipment, for recording parameters, and furthermore can require time for correcting manual data errors that may occur by the engineer during for example the recording. Also, when the maintenance period and specification of the maintenance item is changed, the manager must update the plan of maintenance and the PM sheet; otherwise, the data on the plan of maintenance and the PM sheet may be inconsistent. It is also inefficient for the manager to manually re-schedule all plans of maintenance for such a change. Much time and effort would be invested into manually coordinating the new maintenance requirements with production needs. When for example a manager tries to execute a new plan of maintenance, all engineers must update the maintenance status immediately upon performing the maintenance. Manual management can create inconsistencies between the original plan and the actual result.
Any equipment requiring aperiodic maintenance must be effectively managed to make sure all maintenance will be carried out. Maintenance may be forgotten and the maintenance plan may not be carried out. Under these conditions, the reliability and stability of equipment can be uncertain.
Furthermore, manual management and paper work can waste manpower and paper. Employees using manual management can expend too much effort and waste too much paper in recording maintenance data. Moreover, the paper documents can be difficult to store, query, and analyze. Paper data cannot be effectively used to improve the future maintenance parameters. After a tool is checked and the examiner obtains parameters, the examiner judges whether the tool needs to be maintained. Therefore, there is no schedule for this kind of irregular tool maintenance.
A need thus exists in the prior art to determine the maintenance date for an irregular tool based upon its varying real-time parameters. A further need exists for the automation of the parameter data collection, the calculation of the maintenance date, and the entry of the maintenance date into the maintenance schedule.